Various cleat-pedal attachment systems have been developed for bicyclists with the purpose of providing secure and accurate shoe placement for efficient pedaling. These systems, sometimes called “clipless”, use a cleat with an upper portion that is attached to the underside of the sole of the cyclist's shoe and a lower portion that can be fitted securely into a target position on the pedal. It is desirable that a clipless system also allows the cleat to be easy disengaged from the pedal, whenever the user dismounts from the bicycle in a controlled fashion, but also in the case of a fall.
However, currently available designs require the cyclist to carry out specific, rather awkward, motions of the foot and ankle both to achieve accurate cleat placement on the pedal and to allow the cleat to disengage from the pedal. In many cases, engagement requires careful angular positioning of the foot about a vertical axis (an axis that is perpendicular to the pedal spindle axis, as explained further in the Detailed Description section below), to orient the foot correctly in a plane parallel to the pedal before or while lowering the foot into place. Mechanical forces, provided by torsional elements like springs, are typically used to keep the cleat in place during cycling. In some cases, guidance to the pedal and secure placement at the pedal may be achieved at least in part with the use of magnetic materials. Disengagement then involves either pulling the foot upwards with sufficient force to overcome the attractive mechanical and/or magnetic forces directly, or twisting the foot about a vertical axis, keeping the foot in a plane parallel to the pedal, to achieve a position at which those securing forces can again be overcome. These motions are not easy to perform, especially in a hurry, as the force required for the vertical pull must be significantly greater than the vertical forces exerted during normal pedaling, and the foot twisting process is an awkward one, not well suited to the natural anatomy and kinetics of the foot, ankle, and leg. Other drawbacks with current systems include the use of moving parts, like pivoting latches or springs, which may be adversely affected by exposure to mud, water etc and are prone to wear.
It is therefore desirable to provide a clipless cleat-pedal attachment (and detachment) system that requires relatively simple and natural motions of the foot and ankle, without the exertion of undue force. Ideally, the system would be free of any moving parts.